mySql写法

select * from om_meeting_schedule s where s.is_use=1 
ORDER BY ABS(NOW() - s.meeting_begin_date) ASC
limit 1

oracle写法

SELECT * FROM ( 
SELECT *, ABS(NOW() - startTime) AS diffTime 
FROM om_meeting_schedule 
ORDER BY diffTime ASC 
) C WHERE rownum=1

解释

对于mysql来说ABS(NOW() - s.meeting_begin_date) ASC表示根据差值进行升序排序，然后取第一条